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Men have more willpower than women when it comes to resisting food, a small new study suggests.

"We didn’t expect such striking differences between males and females," study co-author Nora Volkow, director of the National Institute on Drug Abuse, tells ScientificAmerican.com. "Men were able to inhibit their desire for food . . . and women weren’t able to do so."

Scientists had 13 women and 10 men who had fasted overnight look at, smell and taste – but not dig into — goodies like pizza, burgers and cake. They then told the subjects to practice "cognitive inhibition" (read: to try to convince themselves they weren't really hungry) and measured their brain activity using positron emission tomography (PET) scanning. (PET scans measure increases in blood flow linked to brain activity.)

Both sexes reported they felt less hungry when they were trying not to be, according to results published in this week’s Proceedings of the National Academy of Sciences. But the scans suggested that only the guys were able to control their desire to eat. On average, the men showed less activity in the limbic system (the brain’s emotional center that controls the drive to eat) when told to inhibit their craving for food than they did when they weren't told to control their hunger. There was no difference, however, in the women's brain activity.

Specifically, there was a decline in activity in the men's amygdala (an emotional memory region), striatum (a motivation region), hippocampus (another memory area), the orbital frontal cortex, insula and anterior cingulate (which together regulate inhibition, or self-control around food), says study co-author Gene-Jack Wang, a senior scientist at Brookhaven National Laboratory in Upton, N.Y.

Wang and Volkow acknowledge that their findings have limitations. Their sample size was tiny, and the study didn't prove that women are actually more likely to chow down in the face of temptation, since they weren’t given the opportunity. The next step, Volkow says, is to examine "to what extent your subjective perception of whether you can control your hunger or not will predict whether you eat or not. You’d want to determine if, indeed, women will be much less likely to inhibit the food if you put it in front of them. I’d predict that, overall, males may be better."

Some 35 percent of U.S. women suffer from obesity, compared with 33 percent of men, according to the Centers for Disease Control and Prevention (CDC). But women are also disproportionately represented among anorexics, who restrict their food intake to the detriment of their health.

That reality doesn’t challenge the new findings, Volkow says. "For reasons we don’t understand, the female brain is more vulnerable to disorders of feeding, and that can reflect itself in excess or in a compulsion to not eat," she says. "Anorexics are fixated with food, but it is the control over that fixation that becomes reinforcing and motivates their behavior."

Image © iStockphoto/Dean Turner

8 Comments

1. 1. ryansnowden 01:08 AM 1/21/09

   I guess when you try harder to lose weight you resort to things like anorexia and other eating disorders.

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2. 2. splashy 01:44 AM 1/21/09

   If you look at other mammals, the females are the ones driven to eat more. If they don't, the species doesn't survive. Having to try to turn that off is really asking too much of females. It's like trying to tell men not to fight each other over females - it's very difficult if not impossible. The drive is there, and has kept species going for who knows how long.

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3. 3. Ralf123 03:24 AM 1/21/09

   Resist food? I don't get it.
   When I'm not hungry, why should I be attracted by food? A Donut or something similarly heavy would rather cause nausea when I'm full.
   Actually, as a fitness freak, I often have to force myself to eat after a strenuous workout.
   Yeah I'm a guy but I've heard the same thing from female fellow runners.
   

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4. 4. i.s.a. in reply to Ralf123 06:27 AM 1/21/09

   you say you're a fitness freak and so maybe you can't do not exercise. And the same way you need to do exercise to feel good other people need to eat.
   If they are very full they probably can resist but if they're not, even if they're not hungry, they'll feel a desire to eat and, sometimes, they can't control it.
   Some people may eat just because they like to but others will eat because it makes them feel better. food is like a reward or something they take to compensate a bad day.
   I guess women have a harder time resisting food partly because they are more sentimental and they think that a chocolate or a piece of cake will make them feel better. After a while, eating just becomes part of a routine and then they can't stop it. Someday they may realise they're fat, or they will think they are fat, and they'll stop eating at all and become anorexic. Not eating will become part of a routine and so on...
   I'm saying all these because I'm a woman and I've had my share fare of eating problems. I've never been overweight or anorexic but I do have my ups and downs and sometimes I can't stop eating and others I will do everything to try not to eat. And I'm telling it's very hard to control what you eat or don't eat so maybe our brain really plays an important role when it comes to resisting food, whether it's just a psychological thing or the basis of our brain function...
   

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5. 5. pbspbs 06:55 AM 1/21/09

   This study has a ridiculous tiny sample, it doesn't allow any conclusions so any argument around this is based on.... nothing!
   The only thing we learned by reading this article is that someone made a study that doesn't allow us to conclude anything nor answer the question in the title of the article.
   Why publish this? I feel deceived into reading this article.

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6. 6. sonoran 11:22 AM 1/21/09

   Here's an article that doesn't belong in a science magazine. It's epitomizes what's wrong with the current nexus of "science" and popular journalizm. A poorly designed study that really offers no evidence of anything, but deals with sexy subjects "Women wanna eat more!" and brain scans.
   
   Don't get me wrong, I love SciAm... but this story is not worth of space on your site.

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7. 7. dropadisc 12:03 PM 1/21/09

   I am not an expert by any means, but I do tend to have a fairly strong grasp on the human condition. I feel, although this study is not representative of the population due to it's limitations, the point we should walk away with is perhaps not that woman have less self control over matters of diet than men, but rather question wether or not this is a valid query to explore in response to the current percentages of obesity. I personally would like to see more research efforts concentrated on the pressure society places on women to be thin, while accepting the "potbellied" man as a sex symbol regardless of how he looks naked. Furthermore, to say such an article doesn't belong in SciAm is a very limited viewpoint. Any research that may shed light on the psychology of human behavior deserves a place in SciAm- regardless of weather the topic has mass appeal or not. Discovery, insight and forward progress present opportunities to teach and learn- no matter how small the first step may be. Perhaps this article will be the insurgent of further studies responsible for alleviating the population of its obsessions with food as the American pass time, as opposed to it's purpose- to fuel the body and mind.

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8. 8. iconoclasm 01:37 PM 1/21/09

   As far as the choice to publish. It's just basic coverage of BNL press releases. So BNL felt it necessary to mention it and many other outlets covered it. To your point ... some of the conclusions on the BNL site are fairly premature and should have been toned down by BNL (sciam toned it down by not repeating them) . As far as publishing the paper iself, you have to start somewhere. You start with small samples to see if anything is interesting.
   
   What I would like to see is at least some additional or orginal conclusions.
   
   For instance a 2003 UCLA pain study (with a similiar small sample) noted that "[for pain] The female brain showed greater activity in limbic regions, which are emotion-based centers. In men, the cognitive regions, or analytical centers, showed greater activity." They were also careful to say "both responses have advantages and neither is better".
   
   My guess (note the word guess) ... We as people can only quickly change our cognitive regions (freedom of choice). To control limbic responses the cognitive region becomes a guard (disipline) rather than something that can be simple turned off or on (choice). Disipline is less flexibile than and harder to build up than quick choices. Overdisipline of food could be interpeted as anorexia.

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